In general, a paper diaper is composed of cover materials consisting of a water-impermeable sheet mainly for preventing excreta leakage and a water permeable non-woven fabric with good skin touch feeling, containing between them absorbing materials consisting of a fiber material such as cotton-like pulp and fibrous cellulose, and a polymer with high water absorbability such as absorbing paper and polymer absorbing material. When in use, the water permeable non-woven fabric sheet allows water to permeate instantaneously, and the absorbing material absorbs the water to prevent backflow of the water, while the water-impermeable sheet prevents outward leakage of excreta or the water. In this connection, a paper diaper has a merit of no risk of leakage of the water once absorbed due to high swelling by water absorption, but at the same time, it has also a demerit in that it can not be reused by removing excreta differing from a cloth diaper. Thus, a used paper diaper is presently disposed by incineration or in a land fill, which causes various problems in view of environmental preservation, transportation and treatment cost.
With a recent increase in population of the aged, annual demand of a diaper for nursing has increased to about 2.4 billion pieces and is estimated to further increase rapidly in the future. A paper diaper occupies about 97% of the domestic market for adult diapers, and it is foreseen that an environmental problem will become more and more serious in view of waste treatment methods for a used paper diaper in metropolitan areas.
In view of the above situation, various paper diaper processing methods have been proposed. For example, in JP-A-2000-84533, a method is proposed comprising cutting up a used paper diaper by a crusher, followed by breaking up and separating the diaper into components, decomposing a water absorbing polymer to monomers in a decomposing tank charged with calcium chloride to make the monomers water soluble and separating and recovering a pulp component. JP-A-6-502454 (JP No. 3222462) also proposes a method for separating a paper diaper into component elements by finely crushing with a tooth-like blade or the like.
However, these conventional processing methods and processing equipment for a used paper diaper cannot remove excreta sufficiently, because, in all of them, a used paper diaper is broken up compulsorily by a mechanical cutting force using a blade and the like together with excreta, and components of a paper diaper are recovered with simultaneous or subsequent washing. Thus, a large quantity of excreta is left in the components recovered, posing problems such as malodor and hygiene as well as difficulty in processing after that. In addition, since a mechanical cutting force is given during breaking up a paper diaper by a blade and the like, a cover material is also cut. The finely cut cover material is easily commingled into an absorbing material recovered, and it is also difficult to remove it. Therefore, there was a problem that washing and removal of excreta from breakup components of the paper diaper was difficult.
In more detail, excreta and components of a paper diaper such as a broken up cover material and an absorbing material are dispersed in a floating state in a processing liquid in an early stage of a breakup step, but with progress of the step, the absorbing material gradually precipitates and deposits at the bottom part with excreta commingled among them. Once precipitated and deposited, each component never floats or returns to a dispersed state in water again even by intensive washing afterward. In particular, a precipitated fiber material keeps a deposited state, and does not loosen even by newly charging water and immersing after discharging excreta-containing water. Therefore, excreta commingled and precipitated among each component cannot be removed even by repeated washing, resulting in a large quantity of excreta left in components recovered.
In a conventional used paper diaper processing equipment using a rotating drum for breaking up a paper diaper, a broken up absorbing material and the like may clog between the rotating drum and its outer barrel, resulting in troublesome maintenance work in removal of clogged absorbing material. Furthermore, a polymer with high water absorbability highly swells by absorbing water in processing of a used paper diaper, resulting in an increased volume of a used paper diaper charged. Due to this volume change, a size of equipment becomes large in spite of small processing capacity, which also poses a problem in that a wider installation space is needed.
However, it is difficult for a hospital or a care house for the aged, who wishes to install this kind of equipment, to secure wide floor space. Thus, the conventional used paper diaper processing equipment was substantially difficult to be installed.
The present invention has been made in view of such circumstances, and is directed to solve conventional technical problems and provide a method for suppressing the volume increase in processing a used paper diaper. Further, the present invention is also directed to provide a used paper diaper processing method enabling to independently break up a cover material and an inner absorbing material in breaking up a used paper diaper, resulting in enhanced washing efficiency of broken up components and less excreta remaining among an absorbing material.
Further, the present invention is also directed to provide used paper diaper processing equipment enabling efficient separation of a cover material, an absorbing material and excreta, easy removal of cake adhered to a filtering material and the like, resulting in less clogging, easy maintenance, high processing ability and relatively compact sizing.